Apparatus for multiple electric impulse production



TION

' W A. WARD Nov. {15,1966

APPARATUS FOR MULTIPLE ELECTRIC-IMPULSE PRODU( Filed Dec, 17, 1962INVENTOR.

WILLIAM A. WAR D ATTORNEYS United States Patent 3,286,128 APPARATUS FORMULTIPLE ELECTRIC IMPULSE PRODUCTION William Arthur Ward, Norwood, Mass,assignor to United States Scientific Instruments, Inc., Watertown, Mass,a corporation of Massachusetts Filed Dec. 17, 1962, Ser. No. 245,216 20Claims. (Cl. 315241) The present invention relates to methods of andapparatus for multiple electric-impulse production and, morespecifically, to apparatus for producing successive electrical-impulsedischarge, including light flashes for such purposes as stroboscopy orflash photography or the like.

While multiple electrical-impulse discharges have been produced instroboscopes and similar pulse modulator circuits, there is an inherentrestriction upon the ultimate speed of successive discharges residing inthe tendency of the load device to hold over in conduction. The problemof producing very short and rapidly occurring successive electricaldischarges in a single load device, such as a single rapid recoveryflash lamp or similar triggered device, has previously demanded the useof a plurality of separate trigger circuits and associatedenergy-storage circuits. Not only is this costly and complex, but thereis still the possibility of the flash device remaining conductivebetween intended successive discharges; and often the successivedischarges, if produced, will not be of substantially the sameintensity.

It is, accordingly, to the solution of the problem of providing a newand improved method of and apparatus for high-speed multipleequal-intensity electrical impulse discharges that shall not be subjectto the above limitations, that the present invention is primarilydirected. In summary, this end is attained through a pair of criticallyrelatively proportioned energy-storage capacitors charged to differentvoltages and interconnected .by a resonant charging circuit to effect atleast a pair of successive discharges through a common load device, atthe end of which substantially all voltage is automatically removed fromthe load device to prevent hold over or similar phenomena.

A further object of the invention is to provide a novelimpulse-producing circuit of more general utility, also.

An additional object is to provide a novel multiple light-flashproducer, where the term light is intended to embrace both visibleelectromagnetic radiations and longer and shorter wave-lengthradiations, 'as well.

Other and further objects will be explained hereinafter and will be moreparticularly pointed out in connection with the appended claims.

The invention will now be described in conjunction with the accompanyingdrawing the single figure of which is a schematic circuit diagram of apreferred embodiment of the invention.

For purposes of illustration, the invention is described as applied tothe problem of producing a pair of successive substantiallyequal-intensity short light flashes in flash tubes, such as the typedescribed, for example, in'

3,286,128 Patented Nov. 15, 1966 ICC of principal electrodes .3 and 5'between which an electrical-impulse discharge from capacitor C may occurthrough the gaseous medium of the tube 1, in response to the triggeringor rendering-effective of the tube 1 by a trigger impulse applied tointermediate trigger electrodes 5. The trigger electrodes 5 may receivethe trigger impulse through separate isolating capacitive couplings Cfrom a transformer T that is energized by trigger pulses from a triggercircuit 7, as of the type described in the said Letters Patent, or anyother well-known type.

Energy-storage capacitor C (or capacitors) is charged from a voltagesource 2, 4 of predetermined voltage value V (such as a DC. source),through a large charging resistor or impedance R Upon the rendering ofthe normally ineffective or non-conducting tube 1 effective byapplication of a trigger pulse P to the trigger electrodes 5, the energystored or charged in capacitor C will become discharged as an impulse orflash through the tube 1 between the principal electrodes 3 and 5,energizing the tube 1 to produce a flash of light the intensity orenergy of which is related to the magnitude of the predetermined voltageV to which the capacitor C had initially become charged (energy-=C V 2.)

Even were the charging cycle or time constant of capacitor C through Rfast enough, it is difiicult to extinguish and Ie-fiash the tube 1immediately following this first flash because of the tendency of thetube to hold over in conductioni.e., a finite recovery time fordeionizing the gaseous medium in the tube 1particularly in the presenceof the voltage building up in the recharging of C across electrodes 3and 5'.

In accordance with the invention, however, at the same time C wasinitially being charged to voltage V through R a second criticallyvalued capacitor C was being charged from a voltage source 2-4 of valuesubstantially one-half that of the source V (i.e. V/2) through resistoror impedance R By preadjusting the value of C at the critical value ofsubstantially four times that of C (C =4C and connecting a seriesresonant voltagedoubling or boosting circuit comprising inductance L andcheck valve D between C and C the following phenomenon has been found tooccur. After C has discharged its initial charged voltage V, energizingthe tube 1 to produce the first flash therethrough, C will deliver itscharged voltage V/ 2 to C but with double voltage (i.e. a total voltageV) because of the series resonant volt-agedoubling or boosting action ofthe circuit C -LC C then receives a fast re-charge to voltage V, thespeed of which is determined by the half-period of the oscillationfrequency f of the resonant circuit C -L-C (i.e.,

If a second trigger pulse P is applied at T at the end of suchhalf-period, a second energization flash will occur in tube 1 as C againdischarges the voltage V transferred to it from C through L and thecheck valve D. This second flash will be of intensity substantiallyequal to the intensity of the rfirst flash since the same voltage V hasbeen discharged through the tube 1. The inductance L, moreover, ispreferably a sa-turable reactor that effects a short delay in transferof charge from C to C and then, upon saturation, causes rapid voltagetransfer during the half-period of the oscillation frequency f.

At the end of the second discharge, however, since R is made large, asbefore explained, so as to provide a relatively slow re-charging cycleof C through R (C R halfperiod of f), substantially no or littlevoltage, hereinafter referred to as negligible voltage, will be presentacross C and thus at the tube electrodes 3 and 5', so that no hold overis possible. The recharging time of the capacitors should preferably beabout ten percent of the time T required between successive pairs offlashes.

Two very rapid, sharp and equal-intensity flash impulses are thusproduced reliably without spurious hold over and with a single triggercircuit. Provided the same critical relative voltage and capacitorvalues and relation between the resonant charging circuit half-pe riodand multiple trigger-pulse repetition rate are maintained, additionalcapacitors and resonant charging circuits may be added for additionalmultiple pulses or flashes.

As an example, successive pairs of equal-intensity light flashes ofabout 2-10 micro-seconds duration spaced about 350 microseconds aparthave been produced with an FX6A type flash tube 1 (Edgerton Germeshausen& Grier, Inc.) triggered by pulses of about two microsec onds durationspaced about 350 microseconds apart, with C =.33 ,ufarad, C =1.33 farad,V=500 volts, saturable L=5O millihenries, having about 150 microsecondsdelay before saturation, R =60 K ohms, R =l5 K ohms, and

f=1.5 kilocycles (half-period about 350 microsecond-s). The repetitionrate of the pairs of trigger pulses from trigger circuit 7 for producingsuccessive sets of double flashes produced an interval T betweensuccessive pairs of flashes of about 40 milliseconds.

Further modifications will occur to those skilled in the art and allsuch are considered to vfall within the the spirit and scope of theinvention as defined in the appended claims. 'Included in such, is theprovision of a diode D shunting resistor R to prevent overchargingbeyond the value V and clamping the voltage of capacitor C to apredetermined value, particularly in the event that the voltage appliedat 2'-4 is somewhat greater than V/ 2.

What is claimed is:

1. An electric-impulse-prod-ucing apparatus having, in combination,first energy-storage means of predetermined value, a normallyineffective impulse-producing load connected across the firstenergy-storage means, means for storing energy in the firstenergy-storage means with a predetermined voltage, second energy-storagemeans of value greater than that of the first energy-storage means,means for storing energy in the second energy-storage means with afurther voltage less than the said predetermined voltage, avoltage-boosting circuit connecting the first and second energy-storagemeans together, and means for rendering the impulse-producing loadeffective at a first instant of timeito enable impulse energization ofthe load by the stored energy in the first energy-storage means and at asecond instant of time later to enable a second impulse energization ofthe load by the first energysflorage means in which energy has beenre-stored from the second energy-storage means through thevoltageboosting circuit.

2. Apparatus as claimed in claim 1 and in which the secondenergy-storage means is substantially four times the value of the firstenergy-storage means and the further voltage is substantially one-halfthat of the predetermined voltage.

3. Apparatus as claimed in claim 2 and in which the voltage-boostingcircuit is substantially a voltage doubler.

4. Apparatus as claimed in claim 3 and in which the first and secondenergy-storage means comprise capacitors.

5. Apparatus as claimed in claim 3 and in which the voltage doublercomprises a resonant circuit the half vperiod of which is at leastsubstantially equal to the time interval between the said first andsecond instants of time.

6. Apparatus as claimed in claim 5 and in which the resonant circuitincludes a check valve.

7. Apparatus as claimed in claim 5 and in which the said rendering meanscomprises a source of trigger impulses. Y

8. Apparatus as claimed in claim 7 and in which the said load comprises-a flash tube having principal and trigger electrode means with theprincipal electrode means connected across the first energy-storagemeans and the trigger electrode means connected with the said source oftrigger impulses.

9. Apparatus as claimed in claim 5 and in which the charging time of thefirst energy-storage means is greater than the said half-period.

10. Apparatus as claimed in claim 3 and in which the said load comprisesa flash tube having electrodes connected across first energy-storagemeans.

11. Apparatus for producing successive electrical impules, thatcomprises, means for storing at a first location a predetermined voltageto a predetermined capacity, means for substantially simultaneouslystoring at a second location less than the predetermined voltage butwith a greater capacity, means for discharging the stored. predeterminedvoltage at the first location to produce a first electrical impulse,means for transferring the stored voltage at the second location to thefirst location while sub stantially boosting the voltage, and means fordischarging the transferred boosted voltage at the first location toproduce a second electrical impulse.

12. Apparatus for producing successive electrical impulses, thatcomprises, means for storing at a first location a predetermined voltageto a predetermined capacity, means for substantially simultaneouslystoring at a second location substantially half the said predeterminedvoltage with substantially four times the said capacity, means fordischarging the stored predetermined voltage at the first location toproduce a first electrical impulse, means for transferring the storedvoltage at the second location to the first location while substantiallydoubling the voltage, and means for discharging the transferred doubledvoltage at the first location to produce a second electrical impulse.

13. Apparatus as claimed in claim 11 and in which there is furtherprovided first means for triggering a gaseous medium to enable thefirst-named discharging means to discharge through the medium to producea first light flash, and second means for triggering the medium at atime when the said voltage boosting has been effected to enable thesecond-named discharging means to discharge through the medium toproduce a second light flash.

14. Apparatus as claimed in claim 1 and in which the said renderingmeans comprises a trigger circuit for producing successive sets of pairsof trigger pulses for producingdthe said first and second impulseenergizations of the loa 15. Apparatus as claimed in claim 14 and inwhich the time between successive sets of pairs of trigger pulses isgreater than the time for storing the said voltages in the first andsecond energy-storage means.

16. Apparatus as claimed in claim 1 and in which the saidvoltage-boosting circuit comprises a delay device.

17. Apparatus as claimed in claim 16 and in which the delay devicecomprises a saturable inductor that resonates with the first and secondenergy-storage means to effect voltage boosting.

18. Apparatus as claimed in claim 1 and in which means is provided inthe said first energy-storing means for preventing overcharging beyondthe said predetermined voltage.

19. Apparatus as claimed in claim 18 and in which the said firstenergy-storing means comprises a charging impedance and the saidpreventing means comprises a diode shunting the impedance.

20. Electric-impulse-producing, apparatus having, in combination,energy-storage means of predetermined value having highand low-voltageterminals, a normally ineifective impulse-producing load connectedacross said terminals, highand low-voltage energy sources, networksrespectively connecting the highand low-voltage energy sources acrossthe said terminals to store energy in the energy-storage means with apredetermined voltage that, under circumstances of variations of the lowvoltage energy source, may be exceeded at the high-voltage terminalduring the said storing, and clamping means connecting the saidhigh-voltage energy source and the said highvoltage terminal and biasedat the said predetermined voltage for preventing over-storage of theenergy-storage means beyond the said predetermined voltage at the saidhigh-voltage terminals, and means for rendering the impulse-producingload efiective to discharge the said predetermined voltage stored in theenergy storage means.

No references cited.

JOHN W. HUCKERT, Primary Examiner.

10 R. F. POLISSACK, Assistant Examiner.

1. AN ELECTRIC-IMPULSE-PRODUCING APPARATUS HAVING, IN COMBINATION, FIRSTENERGY-STORAGE MEANS OF PREDETERMINED VALUE, A NORMALLY INEFFECTIVEIMPULSE-PRODUCING LOAD CONNECTED ACROSS THE FIRST ENERGY-STORAGE MEANS,MEANS FOR STORING ENERGY IN THE FIRST ENERGY-STORAGE MEANS WITH APREDETERMINED VOLTAGE, SECOND ENERGY-STORAGE MEANS OF VALUE GREATER THANTHAT OF THE FIRST ENERGY-STORAGE MEANS, MEANS FOR STORING ENERGY IN THESECOND ENERGY-STORAGE MEANS WITH A FURTHER VOLTAGE LESS THAN THE SAIDPREDETERMINED VOLTAGE, A VOLTAGE-BOOSTING CIRCUIT CONNECTING THE FIRSTAND SECOND ENERGY-STORAGE MEANS TOGETHER, AND MEANS FOR RENDERING THEIMPULSE-PRODUCING LOAD EFFECTIVE AT A FIRST INSTANT OF TIME TO ENABLEIMPULSE ENERGIZATIONN OF THE LOAD BY THE STORED ENERGY IN THE FIRSTENERGY-STORAGE MEANS AND AT A SECOND INSTANT OF TIME LATER TO ENABLE ASECOND IMPULSE ENERGIZATION OF THE LOAD BY THE FIRST ENERGYSTORAGE MEANSIN WHICH ENERGY HAS BEEN RE-STORED FROM THE SECOND ENERGY-STORAGE MEANSTHROUGH THE VOLTAGEBOOSTING CIRCUIT.